1. Field of the Invention
The present invention relates to an image processing apparatus such as a printer, a copying machine, a facsimile equipment, etc., and particularly relates to an image processing apparatus having a high-speed image processing function.
2. Description of the Related Art
There has been a case where certain image processing is performed upon image data to be transferred to, for example, a laser printer for the purpose of improving the picture quality, reducing the cost of a storage device, and so on. In addition, the resolution of a printer and the speed of printing have been improved recently, and the speed of data transfer has become the most important factor in view of connection of the printer. It has been therefore necessary to increase the speed of data transfer including image processing in order to realize high-speed printing.
As for a system for improving the data transfer speed, a system in which data is compressed by a controller and the compressed data is transferred to a printer to thereby reduce the amount of transferred data is disclosed, for example, in Japanese Patent Unexamined Publication No. Hei. 4-256186. In this system, a compressing circuit in the controller locally reads out image data stored in an image memory, compresses the read-out data, and outputs the compressed data to a printer. In addition, compressed image data supplied from an image input device is expanded by an expanding circuit, and then written into the image memory.
In such a conventional system, there is no device to improve the data transfer speed in compressing processing per se, so that the time taken for the compression decides the maximum data transfer speed to a printer. Next printing is started after passage of the time taken for writing image data into the image memory. Therefore, there has been a problem that high-speed image processing/printing is difficult. In addition, there has been another problem that an expanding device is required to be provided in the printer side.